The present invention relates to an apparatus for opening and closing a wing door and, in particular to an apparatus for opening and closing a wing door of an truck.
Hydraulic actuators or electric motor have heretofore been used as drive power sources for opening and closing a wing door.
If the hydraulic actuators or electric motors are used as a drive power source for opening and closing a wing door, piping, wiring and/or power supplies for driving the hydraulic actuators or electric motors are necessary.
Problems occur that the apparatus for opening and closing the wing door is increased in its scale, that cost and labor are required for its maintenance and that repair is cumbersome if the drive apparatus malfunctions.
It is an object of the present invention to provide an apparatus for opening and closing a wing door, which is simple in structure comprising a spring and a link mechanism, and is almost free of maintenance. It is another object of the present invention to provide an apparatus for opening and closing a wing door in which a force is uniformly applied upon a xe2x80x9cspringxe2x80x9d which is a drive power source for opening and closing a wing door, in which no excessive force is applied to a xe2x80x9cspring rodxe2x80x9d which is connected to the xe2x80x9cspringxe2x80x9d, and which is excellent in reliability and durability.